In an ink jet type printer, an image is formed by discharging ink from nozzles of an ink jet head onto a print sheet. In the nozzle of the ink jet head, there is a concern that the ink is not appropriately discharged because of thickening of ink due to drying of ink inside the nozzle, intrusion of bubbles into the nozzle, attaching of foreign matter such as paper powder near the nozzle, and the like. Here, various technologies are proposed in which the ink is discharged from each of the nozzles regardless of discharging the ink for forming the image (hereinafter, refer to as “flushing”), and thickened ink, the intruding bubbles, and the paper powder in the nozzles or near the nozzles is removed. PTL 1 discloses a technology in which the flushing is performed by discharging the ink from all of the nozzles in a line head printer which performs printing on a belt type print sheet (continuous form) in a period from finishing of printing on a print region of any page to start of printing on a print region of the next page.